Here's a simulation. In this case, DT/H took more time and you took more damage, but the time difference was barely 2 seconds. If you would have dodged all attacks until snorlax used his special, you likely would have come out with more HP with DT/H. I think DB/DP is still playable even though most calcs won't side with it. It really depends how you battle and how good you are. Does it matter being potion/revive efficient if you visit 100 pokestops a day - not really. I think depending on the rarity of dratini in your location, unless you find something "better", both could max this guy out without seeing much of a difference in results.
https://www.pokebattler.com/fights/attackers/DRAGONITE/quickMoves/DRAGON_TAIL_FAST/cinMoves/HURRICANE/levels/28/ivs/FDB/defenders/SNORLAX/quickMoves/ZEN_HEADBUTT_FAST/cinMoves/BODY_SLAM/cp/2400/strategies/DODGE_SPECIALS2/DEFENSE
https://www.pokebattler.com/fights/attackers/DRAGONITE/quickMoves/DRAGON_BREATH_FAST/cinMoves/DRAGON_PULSE/levels/28/ivs/FDB/defenders/SNORLAX/quickMoves/ZEN_HEADBUTT_FAST/cinMoves/BODY_SLAM/cp/2400/strategies/DODGE_SPECIALS2/DEFENSE
First Link is DT/H vs ZH/BS 2400 cp.
Second is DB/DP vs same snorlax.